This invention relates to films, composites, and other compositions that can be made into articles that are disposable through dispersal into waste water under aqueous-alkali conditions and the use of such articles, made from such compositions, as sheet-like materials that have stability during use and disperse into water as a means of disposal.
Even though the amount of plastics used in a variety of consumer goods, packaging and medical articles has not increased over the past twenty years, the visual perception is that more and more nondegradable plastics are filling up our landfills. Plastics offer many advantages over the more traditional wood, glass, paper, and metal articles including improved performance, comparable or decreased cost of manufacture, decreased transportation costs, etc. Disposal of all waste materials including food waste, packaging materials, etc. into a typical landfill provides a relatively stable environment in which none of these is seen to decompose at an appreciable rate. Alternative waste disposal options are increasingly discussed and utilized to divert some fractions of waste from entombment. Examples of these alternatives include municipal solid waste composting, anaerobic digestion, enzymatic digestion, and waste water sewage treatment.
Developing compositions and articles which are more compatible with these waste disposal methods is a goal professed in the current art of plastics improvements.
The art has previously recognized a variety of articles designed for disposal into the toilet or water closet after use, commonly termed xe2x80x9cflushable.xe2x80x9d Flushable articles could, but do not always, totally disperse within the waste water system. They are principally constructed to avoid clogging the waste water system. Non-woven articles of this type are typically useful for feminine hygiene or incontinence. For example, the disposable sanitary products described in U.S. Pat. No. 3,480,016 are comprised of fibers bound together by a resin which is insoluble in water but will disperse due to water sensitivity upon disposal into the toilet. Similar structures are claimed in U.S. Pat. No. 3,804,092. Alternatively, composite flushable structures for feminine hygiene articles include those described in PCT Publication WO 91/08726 wherein an absorbent core of fibrous material is laminated to a water permeable topsheet and a water impermeable backsheet. The topsheet may be a film or a non-woven and both the topsheet and backsheet were described as comprising polylactide or polyglycolide. Similar composite articles and uses are described by U.S. Pat. No. 5,300,358.
There exists art describing a variety of flushable articles comprised of film structures. For example, a bedpan liner was described in U.S. Pat. No. 3,546,716 which is made from a cold water soluble base film, e.g. poly(vinyl alcohol) film, coated with a water insoluble or water repellent material. The structures also contain a tissue paper covering adhered to the water insoluble coating and the preferred disposal is into the sewage system.
Another series of articles designed to be flushed into sewage treatment is described by U.S. Pat. No. 4,372,311 wherein disposable articles comprised of water soluble films coated with an insoluble material are claimed. Articles may be useful as feminine hygiene products, diaper components, or bandages. The existence of a laminate structure was noted, this being that when the coating was of sufficient thickness to have film-like properties unto itself.
The use of a water soluble film coated with or laminated to a water insoluble film as a disposable bag is described in U.S. Pat. No. 4,620,999. The claims describe a package for body waste which is stable to human waste during use but which can be made to degrade in the toilet at a rate suitable for entry into a sewage system without blockage by adding a caustic substance to achieve a pH of at least about 12. Such structures are typically a poly(vinyl alcohol) film layer coated with polyhydroxybutryate).
A related structure is described by PCT Publication WO 92/01556. A multilayer film containing layers of water insoluble and water soluble films is described, where both layers may be made from poly(vinyl alcohol) and a difference in the extent of hydrolysis provides the differential solubility. The mechanical strength of the composite comes from the water soluble component and the resistance from water during use is derived from the water insoluble coating. Uses envisioned included diapers, cups, golf tees, and laundry bags. A later publication WO 93/22125 describes the process for making these structures and lists additional article claims for sanitary articles and articles where the insoluble coating is specifically an ink.
Compositions comprised of multilayer films are known in the art. The utility of such structures lies in the manipulation of physical properties in order to increase the stability or lifetime during use of such a structure. For example, U.S. Pat. Nos. 4,826,493 and 4,880,592 describe the use of a thin layer of hydroxybutyrate polymer as a component of a multilayer structure as a barrier film for diaper components and ostomy bags.
Others have designed multilayer films specifically to be compostable. PCT Publication WO 92/15454 describes films which are comprised of external layers of an environmentally degradable film and an internal layer of a biodegradable, water soluble film. Typically, the external layers are comprised of a polyolefin, poly(caprolactone), or ethylene vinyl acetate and the internal layer is described as poly(vinyl alcohol). One of the external layers may be a non-woven structure. Additional art in this area is described by EPO Publication 0 616 570.
The development of a multilayer microfiber has been noted in the art. Basic technology building patents describing the process by which multilayer microfibers can be prepared are described in U.S. Pat. No. 5,207,970.
Disposal of medical waste is increasingly coming under the scrutiny of government agencies and the public alike. Concerns over the fate of materials contaminated with infectious substances are valid and proper measures to insure the safety of health care workers and the general public should be taken.
Currently, medical, waste can be categorized into reusable and disposable. Reusable medical articles are cleansed and sterilized under stringent conditions to ensure disinfection. For example, reusable medical devices such as garments or drapes can be used up to 100 times. In comparison, after use, disposable medical articles are typically disinfected or sterilized, adding a significant cost, prior to disposal into a specially designated landfill or waste incinerator. Often, the disposal cost for the contaminated single use articles is quite high.
The utility of a water dispersible tape for use on reusable surgical drapes and gowns was recognized in U.S. Pat. Nos. 5,125,995 and 5,270,111. The use of a water dispersible indicator tape was recognized in PCT Publication WO 93/24152.
Furthermore, a series of U.S. Patents describes composite fabrics, utensils, packaging materials and a method for disposing garments and fabrics which are soluble in hot water, namely: U.S. Pat. Nos. 5,268,222; 5,207,827; 5,181,967; and 5,181,966. The structures described are typically comprised principally of poly(vinyl alcohol) which is only soluble above 37xc2x0 C. The target disposal method for said articles is via laundering where the temperature is usually greater than 50xc2x0 C.
Similar fabrics are described in Canadian Patent Publication 2,093,051. A composite structure of non-woven layers is prepared from a poly(vinyl alcohol) component and another material which acts as a barrier layer during use. The non-woven fabrics claimed are designed to disperse in an aqueous environment having a pH greater than 12 and a temperature greater than 70xc2x0 C. in a period of less than about 10 minutes.
Generally, poly(lactic acid), its blends and several articles made thereof are described in U.S. Pat. Nos. 5,200,247; 5,227,415; 5,076,983; 5,216,050; 5,359,026; and PCT Publications WO 94/06866; WO 94/07941; WO 94/08078; WO 92/04412; and WO 92/04410 and references cited therein. No references to the utility of poly(lactic acid) in a laundry dispersible article were described.
Poly(ester amide)s are described in a series of patents by Barrows, et.al. in U.S. Pat. Nos. 5,286,837; 4,529,792; and 4,343,931. The utility of such materials in a laundry dispersible article was not realized.
The art has recognized the use of water soluble or alkali-dispersible materials or combinations thereof for articles, which can be disposed via flushing into waste water. However, the art has not recognized that novel compositions and materials and existing compositions and materials can be employed to provide a single use article that is effectively dispersed via hydrolytical degradation during a single commercial laundry cycle.
The present invention relates to the development of compositions and articles for disposal into the waste water treatment process, specifically via dispersal into an aqueous-alkali environment accompanied by elevated temperature or elevated pH or both and can include mechanical agitation.
The present invention solves the problem of disposal of articles by designing materials for a single use and then for disposal into the laundering cycle. Thus the transportation and handling costs and risks associated with disposable medical articles and the risk of incomplete disinfection of a reusable article can be eliminated.
The present invention has found that novel and existing compositions and materials can be employed as this type of article which resolves the issues confronting both single use article disposal and multiple use article recycling.
Compositions used in the present invention can be constructed from a variety of polymers and can be constructed in a variety of forms. Some of the compositions are themselves novel and some of the forms of construction are novel. All of the embodiments of the invention are novel in their use as alkali-aqueous disposable articles.
Compositions used in the invention comprise hydrolytically degradable polymers. Consistent with the definitions employed by the American Society for Testing of Materials D883 Standard Terminology Relating to Plastics, xe2x80x9chydrolytically degradablexe2x80x9d means a degradable plastic in which the degradation results from hydrolysis. A xe2x80x9cdegradable plasticxe2x80x9d means a plastic designed to undergo a significant change in its chemical structure under specific environmental conditions resulting in a loss of some properties that may vary as measured by standard test methods appropriate to the plastic and the application in a period of time that determines its classification. It is significant to the invention that hydrolytically degradable polymers not only disperse in aqueous-alkali conditions of a laundry but also can degrade in waste water over time regardless of pH.
Nonlimiting types of hydrolytically degradable polymers include poly(lactic acid) (hereafter xe2x80x9cPLAxe2x80x9d); poly(ester amide)s (hereafter xe2x80x9cPEAxe2x80x9d); poly(glycolic acid) (hereafter xe2x80x9cPGAxe2x80x9d); and poly(hydroxy butyrate-co-valerate) (hereafter xe2x80x9cPHBVxe2x80x9d); and the like; and combinations thereof as copolymers, blends, mixtures, and the like.
Some compositions of the invention also comprise hydrolytically degradable polymers in combination with water soluble polymers. xe2x80x9cWater solublexe2x80x9d means that the polymer will completely dissolve upon extended contact with water. Nonlimiting types of water soluble polymers include poly(vinyl alcohol) (hereafter xe2x80x9cPVOHxe2x80x9d), poly(aspartic acid), poly(acrylic acid), poly(methacrylic acid), poly(acrylamide), poly(vinyl pyrrolidone), poly(alkylene oxide)s, complex carbohydrates, and combinations thereof as copolymers, blends, mixtures, and the like.
Constructions of compositions used in the present invention can include single layer films, multiple layer films, non-woven webs formed from staple fibers, non-woven webs formed from single layer microfibers, non-woven webs formed from multiple layer microfibers, non-woven webs formed from microfibers of blended compositions, and non-woven webs formed from sheath-core microfibers.
The type of composition and the type of construction used in the present invention can be chosen according to the type of features desired for the aqueous-alkali dispersible article.
Articles of the present invention can have the following features. The article can be dispersible, and hence disposable in wastewater, when exposed to water having an elevated temperature. xe2x80x9cElevated temperaturexe2x80x9d means greater than or equal to 50xc2x0 C.
The article can be dispersible, and hence disposable in wastewater, when exposed to water having an elevated pH. xe2x80x9cElevated pHxe2x80x9d means that the pH is greater than7. Preferably, the pH is greater than 9.5 and need not exceed 11.9 because each of the articles of the present invention will disperse at elevated temperature and during a single commercial laundry cycle into waste water at a basic pH less than 12. Commercial laundries generally avoid laundering at pH of 12 or greater because reusable fabrics can be damaged, especially polyesters.
The article can be dispersible, and hence disposable in wastewater, when exposed to water for a minimal time, such as used in a single commerial laundry cycle. xe2x80x9cSingle commercial laundry cyclexe2x80x9d means a cycle of soaking, agitation, spinning, rinsing, and spinning that comprises about 40 minutes with the soaking and agitation durations comprising about 30 minutes.
The article can be sturdy and resistant to water during preparation, storage, and use. xe2x80x9cWater resistantxe2x80x9d means that the article will not significantly degrade upon contact with water, saline solution, or human body exudate such as perspiration, blood, urine, or other bodily fluids yet will be dispersible and hence disposable when exposed to water in a single commercial laundry cycle.
xe2x80x9cAqueous-alkali dispersible articlexe2x80x9d means that at elevated temperature, elevated pH, and that during a single commercial laundry cycle, the article substantially degrades into small pieces and substantially disperses into water. Preferably, the substantial degradation is at least 90 weight percent of the article. The small pieces should be capable of passage through the mesh screens and other filtering devices typically associated with commercial laundry facilities. Typically, the mesh screens and filtering devices can permit passage of pieces of a size not larger than about 25 mm and preferably not larger than about 12 mm and most preferably not larger than 7 mm. The smaller the size of the pieces, the easier it is for the pieces to continue to hydrolytically degrade in the waste water regardless of pH.
A feature of the invention is that the articles of the invention are dispersible in an aqueous-alkali environment and yet are resistant to water during use. The articles can be formed from at least one hydrolytically degradable polymer or from a combination of polymers where one polymer is hydrolytically degradable and one polymer is water soluble. The articles function well during use because the hydrolytically degradable polymer is either water insoluble or water impermeable and prevents the water soluble polymer from dissolving upon contact with liquids or bodily fluids. Upon disposal, the water soluble polymer will enhance the rate of dissolution or destruction of the article in the aqueous-alkali environment, especially when exposed to some combination of elevated temperature, elevated pH conditions of a single commercial laundry cycle. The hydrolytically degradable polymer portion of the article will hydrolyze or otherwise degrade, allowing the water soluble polymer to dissolve and result in the entire article breaking up and dispersing into wastewater.
Another feature of the invention is that an article of the invention entirely disperses into water within a short time, at least no longer than a single commercial laundry cycle, to easily dispose of the article that has been used. The laundry cycle is known to disinfect contaminated materials; therefore there is no hazard associated with discharge of the waste water containing the dispersed article. Indeed, the wastewater can further hydrolytically degrade the hydrolytically degradable polymer, if necessary, regardless of pH. This disposal method is more convenient than if the contaminated article were to remain a solid waste requiring disinfection prior to disposal into a landfill or waste incinerator.
Another feature of the invention is that either existing compositions or constructions can be used in a new article to provide the aqueous-alkali dispersible article as used according to the present invention. Unexpectedly, some hydrolytically degradable materials will undergo sufficient degradation within one laundry cycle that the articles made therefrom can be considered dispersed.
Another feature of the invention is that novel compositions and constructions can also be used in the new aqueous-alkali dispersible articles.
Another feature of the invention is that hydrolytically degradable polymers can be used alone or with water soluble polymers in the constructions used in the invention.
Another feature of the invention is that the constructions used in the invention can be combined with reusable medical devices where only the dispersable portion of the combination is disposed while the reusable portion of the combination is recycled. The recycling and the disposal can occur in the same laundry cycle.
An advantage of the invention is that compositions and constructions of the present invention are easily manufactured.
Another advantage of the invention is that the compositions and constructions of the present invention are flexible, conformable to the mammalian body, and not irritating or allergenic to mammalian skin.
Another advantage of the invention is the ability to use the present invention to alter the manner by which articles contaminated by infectious waste are disposed from solid waste landfilling or incineration to wastewater treatment.
Briefly, one aspect of the invention is an article comprising an aqueous-alkali dispersible microfiber comprising at least one hydrolytically degradable polymer.
Another aspect of the invention is the use of a water resistant, aqueous-alkali dispersible article dispersible at elevated temperature, elevated pH, and during a single commercial laundry cycle, wherein the article comprises at least one hydrolytically degradable polymer.
Another aspect of the invention is a multilayered microfiber, comprising at least one layer of a water soluble polymer and at least one layer of at least one hydrolytically degradable polymer.
Another aspect of the invention is a sheath-core microfiber, comprising a water soluble polymer core and a hydrolytically degradable polymer sheath.
Another aspect of the invention is a method of disposing of a water resistant, aqueous-alkali dispersible article comprising at least one hydrolytically degradable polymer, comprising the step of subjecting the article to elevated temperature, elevated pH, and a single commercial laundry cycle, whereby the article disperses into wastewater.
The embodiments of the invention are further described below.